In known loader/backhoe equipment there are as many directional control valves as there are cylinders and when the loader boom and bucket directional control valves are in use, the remaining cylinders and directional control valves are idle, and similarly when the backhoe boom, dipper, bucket and swing directional control valves are in use, the loader boom and bucket directional control valves and the stabilizer directional control valves are idle, the latter having already been operated to set the stabilizers in ground-engaging position.
Accordingly, in known loader/backhoe or like dual hydraulic systems, it is quite expensive, not only from the standpoint of numbers, to include as many directional control valves as there are functions, but especially in those cases where the directional control valves incorporate therein load check valves, overload relief valves, makeup check valves, and/or pressure compensators.